“We’re both Christian and it’s in the Bible,” said Ms. McIntyre, when asked if she shared her co-author’s concerns.

Convincing Christians that radio tags are a glide path toward the end of days may be a stiff challenge. For example, the Bible specifies that the mark of the beast will appear in the right hand or forehead, both impractical sites for human implants, according to tag vendors like Applied Digital. And as the authors concede in “Spychips,” the Bible says the mark is 666 and “we’re not sure how the 666 part fits in.“